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Old Jan 21, 2013, 08:16 PM
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John235's Avatar
Sydney, Australia
Joined Mar 2006
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Rob, Interesting to see your model. I think its unusual because the canard is very low aspect ratio (short span, large chord) compared to the main wing. I think it is also generating some lift from the body of the model. When flying at high alpha I think you are probably pushing the main wing towards tip-stall, which would explain the roll instability.

If it was my model I would experiment with a new canard wing with larger span, and maybe a little bit less chord depending on the actual dimensions. If the canard is well designed and CG placement is correct there shouldn't be a problem with tip-stall of the main wing, because the canard wing always stalls first.
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Old Jan 21, 2013, 08:39 PM
Takeoff=Option Landing=Must
robusp's Avatar
USA, NY, Depew
Joined Jan 2009
788 Posts
Chrizz,
You are right. After I cut it down I am closer to 20-40% of main wing.

I wasn't even aware of different types of canards.

I will look in to it before re-maiden.

I might even have an issue with thrust angle of the motors.
They are 1 deg down. My EDF PJ flies excellent, but I had to fix the angle first. It is 0 deg now. For comparison original PJ with pusher prop had to have 1 deg down.

John235,

Canard was originally lot bigger. (look at picture 1)
It was easier for me to cut the span, than chord.

Rob
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Old Jan 21, 2013, 09:57 PM
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Denmark, Central Denmark Region, Silkeborg
Joined Nov 2009
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Hi robusp!

I just thought of another very, very (can't stretch this enough) recommendation:
To always perform glidetest to verify aerodynamic-concepts before even trying to fly under power, on any aircraft.
I don't want to bother you with all kind of recommendations, but making unpowered glidetest allows to separate the understanding of a flight-envelope's aerodynamic capabilities from eventual, undesired, effects due to applied thrust.

Happy landings :-)


PS In the same spirit, while doing glidetests, one shouldn't have to correct a planes path by piloting-input either. Overcorrecting by piloting-input will often lead to mis-readings of situations and flight-capabilities. A plane should, more or less, be able to sustain flight on its own.
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Old Jan 21, 2013, 10:29 PM
Takeoff=Option Landing=Must
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USA, NY, Depew
Joined Jan 2009
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Chrizz,

This might be little difficult.
At 24" (610 mm) wing span, 28" (710 mm) long and 18 oz (510 g) weight, I don't think I can throw it hard enough to stay in the air.

Rob
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Old Jan 21, 2013, 10:42 PM
Just Me
United States, OR, Salem
Joined Apr 2006
817 Posts
Quote:
Originally Posted by robusp View Post
Chrizz,

This might be little difficult.
At 24" (610 mm) wing span, 28" (710 mm) long and 18 oz (510 g) weight, I don't think I can throw it hard enough to stay in the air.

Rob
Find a hill and throw it down slope, that should give it enough air and you enough time to determine what it's doing.
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Old Jan 21, 2013, 11:18 PM
Takeoff=Option Landing=Must
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USA, NY, Depew
Joined Jan 2009
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Hey, I hear you guys.

By any means I am not an expert pilot or a builder.
This plane is my 5th scratch build contraption. I guess I got lucky so far. Every project is something totally different.
My record is pretty good. All of them are pleasure to fly.
Most of the time I can tell what I need to change, after maiden flight or two, or three.

In this case, I think if anything it should fly better than last time. It was a hand full, but I brought it back and made adjustment and flew it again.

I took some pics from all angles.

Next project I am working on I'll try toss. I actually never thought about it with this model.

Rob
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Old Jan 22, 2013, 02:54 AM
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Hampshire, U.K.
Joined Jun 2008
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As others have already said, when you get into the high alpha attitude, those wing tips begin to stall, as evidenced by the rocking. What's more, they are the rearmost lifting surfaces so, once you lose those, the centre of lift moves forwards, so suddenly your plane is tail heavy and, because of the low airspeed, the elevator may not have enough authority to push the nose down.

My guess would be that you need to move the cg forward a bit and, in view of the high wing loading, use a fairly powerful bungee launch to get the wing flying properly. Good luck.
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Old Jan 22, 2013, 03:55 AM
What could possibly go wrong?
nickchud's Avatar
Market Harborough
Joined Apr 2006
3,652 Posts
Here's a video of a plane doing something very similar to what you describe. However... 470watts and 18 oz, blimey! My plane had a very low wing loading, so I actually had quite a bit of fun with the aft CG. There was a lot of lift from the body and I bet yours does too. In the end, I took the canard off, gave it a hull and mounted the motor and elevator on the tail. Same plane, but actually she flew better. Sorry to say that, being a canard fan myself.


stuntcat Canard Maiden Flight (2 min 39 sec)


Polaris Stuntcat Flying (4 min 2 sec)




PS I wonder if bigger fins might help with yours. They look quite small and there's quite a lot of lateral area in front of the CoG, especially until you move it forward.
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Old Jan 22, 2013, 06:10 PM
Lighting Up the Darkness
United States, GA, Loganville
Joined Jan 2013
23 Posts
Greetings canard fans. Does anyone know where I can find a good set of plans for the Long EZ? Raidentech.com has a pretty nice ARF (to be in stock in about 3 weeks), but I'd really like to build one.
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Old Jan 23, 2013, 05:41 AM
What could possibly go wrong?
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Market Harborough
Joined Apr 2006
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Hello NightLight, Greetings.

On the previous couple of pages we had some traffic about the Long EZ. If you're thinking of building a small one with balsa, you'll find the link to my build thread. I've had quite a lot of experience since those days and I'm currently drawing up some plans for a quarter scale EZ made from Depron.

Are you considering balsa or Depron? I reckon that it's possible to do a nice job with Depron and don't forget, the full size plans by Rutan were for a plane built from foam and fibreglass.

Here's a model with complex curves that was built from Depron and WBPU. It's a Republic Seabee.




I'll post my plans as soon as I have something to show and I'll start a build thread when I get round to it... quite soon I hope.

Cheers

Nick

PS that's not my Seabee, it's a beauty isn't it. Im building one just now.. Here's the thread.
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Old Jan 23, 2013, 11:07 AM
Lighting Up the Darkness
United States, GA, Loganville
Joined Jan 2013
23 Posts
Thank you Nick. The Depron material is quite interesting. I have some building experience with balsa and solar film covering, but I've never used Depron. What are you using for adhesive?

Kind Regards,
Russ

and thank you for the pictures! The Republic Seabee project was shaping up nicely! It really shows the potential of the Depron material.
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Old Jan 23, 2013, 01:12 PM
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Denmark, Central Denmark Region, Silkeborg
Joined Nov 2009
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Hi nightlightrepair!

A good glue to use with Depron (and in many other cases too) is UHU Por.

PS Depron is a fantastic building material!!
On a side note: Notice that it's strongest (and therefore also less flexible) in one direction due to the fibers composing its outer skin running that way. The fibers are running the same way as the printed text on the sheets. Good to know...
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Old Jan 23, 2013, 01:19 PM
What could possibly go wrong?
nickchud's Avatar
Market Harborough
Joined Apr 2006
3,652 Posts
Yes, UHU Por is really good stuff. I'm not sure if you can get it easily in the States. P'raps someone here can suggest an alternative. And Gorilla Glue, white if you can get it. The G G fills gaps very well and gives you time to position things. I definitely don't get on with the glue gun or with foam safe CA. Too brittle for my liking and the CA costs loads more than the others.

My Depron doesn't come with printing on it, but it is possible to feel which way the 'grain' runs.

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Old Jan 23, 2013, 07:22 PM
Lighting Up the Darkness
United States, GA, Loganville
Joined Jan 2013
23 Posts
Chrizz, Nick: Thanks for the recommendations regarding Depron. VERY good to know regarding the strength properties related to the grain of the fibers. I'll experiment and contemplate a canard related project. I'm going to do a little research on the availability of the adhesives you suggest as well. Thank you.

I am preparing to embark upon my first canard build. I may very well be more of a canard addict than the canard addict himself! I've printed off Charles' great information regarding the GWS stick conversion at the very beginning of this thread and I believe I have just about everything I need to start the project. I'll post some pictures as I go along and, of course, I welcome your thoughts and recommendations.

Kind Regards,
Russ
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Old Jan 23, 2013, 08:11 PM
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Chrizz's Avatar
Denmark, Central Denmark Region, Silkeborg
Joined Nov 2009
726 Posts
Hi again!

While at talking Depron...
Here's another thing that's good to take into consideration: Depron is a laminate.
It consists of two layers of some kind of plastic-foil with foam in between. Its strengh is also the result of that.
This is worth talking into consideration when building: i.e. if sanding the surface of a sheet of Depro, it will loose some of its strengh, rigidity, in a non-proportional way, when the plastic-foil thins of.
Another interesting fact, when comparing the weight of different Depron thicknesses (1mm, 3mm, 6mm...), is that the weight increase isn't proportional to its thickness. I.e. 1x6mm is lighter than 2x3mm because of its laminate construction.
It's not "just" foam...
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